The Philadelphia Zoo - Primate Reserve

Here, gorillas, orangutans, lemurs, langurs, gibbons, and colobus monkeys go about their routines of playing, eating, and sleeping in plain view of visitors.

Visitors can see an orangutan play tag with a gibbon, or see a mother spectacled langur give her baby to one of its older siblings to babysit while she takes a rest. A huge male gorilla often takes naps very close to the glass where visitors can see the outdoor exhibit.

And the female gorilla can often be seen observing visitors.